Every field that you enable becomes a column. Conversely, if the field is not available as a column heading, you can't view or edit that field.

It would be great if we had the ability to specify which fields are visible as columns in each View, and still have access to all the fields when viewing the task details. But that would involve a change from the spreadsheet format.

The Multi-Line format is a partial solution but it doesn't provide enough info when viewing the task list.